I don't want to open up the whole can of worms again, but there are times when I've found a debugger really helpful. I usually start with simple print statements, but sometimes I'm working in an environment where running the program to get to the problem area takes a long time, and if I guess wrong about what to print out it can take forever to do another iteration. That's when it's nice to be in the debugger, poking around wherever I like, stepping forward a bit if necessary.